Inserting tool for push-in inserts



June'24, 1958 J. BRANCATO 2,839,823

INSERTING Toor. FOR PUSH-1N INSERTS Filed May 25, 1955 l -37 /0 V f/r 25 1 29 L x 55 a a0 /26 /5 1 I 1 52 /3 l y sa 5/ 50 ,d /9

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. E J. BRANCA ro ATTORNEY Y MSM/m which the triangles are erected.

inserticoil'when -SuLfeLq .I 1 Euntherobjects and ,details otl` theinventionzwilll e: apparent from-"the descriptioirgivenrhereinafter' and'ithe 1.'

United States Patent 12339323 iNSERTING root Fon PUSH-IN INSERTS Leo J. Brancato', Danbury, Conn., assigner to Heli-Col Corporation, Danbury, Conn., a corporation of Delaware Application May z5, 195s, serial No.. 511,026 vs claims. (CI. 2st-27s) The invention relatesto an inserting tool for push-in tain articles of plastiqniaterial, the wearresistant properties of a screw thread provided in a hole is of higher importance thanthe strengthofthe thread. In many iustances'where thisis the case, itis also required that the costs are reduced as. far as possible, Whereforetlie conventional, time and labor consuming steps of tapping a thread in a hole of the boss or nut member and, then,

screwing the insert into such tapped thread, are objectionable. Nevertheless, the screwthread forming wire. coil can be advantageously used in such cases if a suitable insert is pushed in the axial direction .into a` cylindrical hole and held there suihciently firmly by friction.

The wire of -acpiltr the mentioned purpose has. a crosssection preferably composed off-an inner and an outer triangular portion v.and a rectangular portion on In an insert of such type, the inner triangle forms-'the screw thread intowhich a, member with a corresponding eitternal thread can be screwed. The outer triangle of the coil wire crosssection bearing against the inner wall of a cylindrical hole creates avdesirable high frictional resistance to a vmovement in the axial and the peripheraldirections if .the insert. is. .originally coiled slightlyoversized, and the intermediate rectangular portion provides surfaces with which thef coil convolutions can b ear upon. one 'another and take up the axial thrust applied for pushing the coil into the cylindrical hole. However, Ihave foundvthat certain difficulties are ,en-

2,839,823 Patented .time 24, 195s 2 accompanying drawing illustrating an embodiment thereor` by way of example.

Inthedrawinaf., f l Figi 1 is alongitudinal cross-section of a tool according ma@ invention.

Fig.2is an end elevationthereof, Figs. 3 and 4 are crosssections' along lines 3-3 and 4 4, respectivelyptia-l- Fig- 5. is. .an.enlarged.e1evari0xi,.fpart1y. in station...0.f portion of theto'ol of Fig. lasv applied to a boss during the insertingproess,

Fig. 7 is a crosssection o famodified tool head.

Referring now to the drawing, the tool illustrated ijn Figs. lito 4 comprises a .tubularr shell 10 in which`, a mandrel 12 is rotatable. and'gaxially movable. Near ,the foot end; of the shell, afrecess- 13 is-providedwhichextends 'through` 180 of. the shell periphery and lengthwise somewhat more thanthelongest coil tobe inserted .bythe tool. An axial slot I4 isI provided whichI reachesfrom'the recessl'to the ultimate end of the shell whei'ea smal-l edge-1ike .rim 15 .projects from the end. facejltz, This rim has. an inner d i-ameterequal tothat of tlie;endfpor, ,tion 1710i theshell wl 1 ich -includes .the recessed andthe slotted 'parts. The outer surface 15. ...of the. rimslant s upward to, ak maximum .diameter which .is. ver-y .muh' .smaller than that. of the face 16.. The shell portion o pposite the recess. 13 isprjovided with ae rather wide .groove .1S in which a spring .19.is .embedded andheld to ,theshell by its radial"A projections 20 -nd., 21..as rclearlyshown sin Fig. 3. f Fora purpose to 'be explained later,"1 a portion 2 2 of thespring extendsfroxnthe projection 21 at an-jangle into. the, recess 13a` To the free end of `theportion- 2 2 a. springwire 23 issecured e. Vg.v by soldering sofas-to engage` in the slot.1f4..and bear againstfthe lower portion countered when aninsert coil. ofthernentionedftype is l pushed home. QOnthe one hand, care must beI takenthat v during the applicationof the insertingpressure. none-,of

the coil convolutions devi-atesfrorn the true axialposition,

on theother hand. the coil must be prevented-.from expanding due to the axial pressure which has to be applied.

Therefore, the object of'the invention is. the vprovision of a toolgfor pushing a-slightly oversized wire co'il insert into a cylindrical-,1101;.whereinvthe toolf includes: means for preventing theinsert from tiltingzandvmeans; foripreventing the last convolution from springing. out. duringV the inserting process.

The invention also aims to provide a tool ofthnieniioiled type .which preventstan undueE expansion off the 24 of the mandrel, l`his-portionl24- is ofaslightly smaller diameter thanthe-,majorvmandrelportion25. .Correspondingly, the portion v17 of the she1lis ofa smaller .inner diameter.thanvther major shell portion 26, sonthat to a slot .33 as'clearlylshown inI.Fig; 4. Asnap ring 34 engages in the; bore -32fand groovel 31'and.projectsfwi th its free' end 3 5L intohthe. slot 33 so: as tobear. ag'ain'sti'the mandrel'. The. mandrel maybe providedk witlra: shallow groove 36 opposite slot 3-31 in theillustrated position so that the lend 35 mayy engagethat groove'ini order topre- -vent `the mandrel fromwshifting in relation tothe Ishell when the tool'is-vn'ot in use. By turning the man'drelT-in the shell, .thezendr 35 Willfbe urgedout of'groove 361 Aso thatthe mandrel can be freely sliiftedFin` the aXial'direction. If, 'then,1 the mandrel' is Ypulled upwardgflits4 end position is reachediwhen' the snap ring end 35A comest'o it isf subjected'. to the-axial inserting pres- 'bearagainst'thel shoulder 30'. i When,`thereatter, the' manrdrel-is pushed down,i'the end35= can slide on -the'co'nical surface of the portion.29` Without inhibiting such movement; The dist'anceo'fwe .shoultlerv 30 from thegl'ead 2 7.

isso-sel'ected 4that the1 lowerm'ost endf of the mandrel in its upperl end position has fully cleared the recess' 13;

The diameter 'ofi the' lower:portion 24' of theema'ndel and the eorre'sporidingy inner diameter"of;A tli'ejshell por- Vtion 17V are made substantially-equal'to the outer d ametr of; a 'coil to be insertedtbyv the tool.v Fromthe'portion'zkl a short co-axial piece 37, and from the latter a'longer co-axial piece 38'extend, each with a smaller diameter than the preceding piece. The diameter of the piece 38 is very slightly smaller than the inner diameter of the insert coil after its insertion, and'theshoulder 39 between the pieces 37 and 38 is of such a width that it can bear on the at surface of the coil wire cross-section as it will be fully apparent from the description given hereinafter with reference to Fig. 5. The shoulder 39 is helically shaped in accordance with the top convolution of the coil, and has a straightstep 40 which can bear against the end of a coil slipped on the piece 38.

The Voperation of the tool is illustrated in Fig. in which a boss member '50 is provided with a cylindrical hole 51.- The hole is countersunk at its upper end at 52. In order to provide the hole Vwith an inner screw thread, a wire coil 53 is produced which has a wire crosssection Vasstated hereinbefore, preferably consisting of an inner'and an outer triangularportion, 54 and 55, re-

spectively, and a median rectangular portion 56. However, it wil be understood that the toolv according to the invention is useful for coils of suitable other wire.crosssections too. To'apply'the coil, the mandrel 12 of'the tool is iirst retracted vinto itsV upper end position in which the end 35 of the snap ring 34 stops Vthe shoulder 30. Thereby, the recess 13 is fully cleared of the mandrel and thev coil "53, of adequate length and diameter, can now be inserted'into the recess 13 between the spring portion 22 and the shell portion'17.""lhereupon the mandrel 12 can be pushed down rst so far that the end portion 38 enters the interior of the coil which comes to bear against the helical face 39 of the tool. j By turning the mandrel 12,'the step 40 will be brought into Vengagement with the upper end of thecoil so thatthe entire top convolution of the coil bears'against the helicalface 39,'as clearly shown in Fig: 5; The coil `53 will not turn with the mandrel beforethe step 40 engages the coilend and unless the mandrel is turned in the direction the coil is wound,A because thew spring arm 22 sets up sufficient friction'to hold-the coil bacioy The tool with the coil there Vin may then'be set up coaxially with the hole 51 so thatY thel edge V engages into the countersunk portion 52. During thisoperation,` spring 23 assures that the coil will remain in-contact with'th'ey shoulder of the mandrel when Ythe tool is held in a vertical position Vand prior to the installation of the coil in the hole. Without spring 23 it-might happen that the coil falls out of the sleeve as V.soon as vthemandrel-is advanced if at that time the free coil end is notryet in V engagement with Vthe hole. It', will -be.noted vthat-the inner diameter of the shell portion f 17, which is equal to kthe outer diameter of the coil 53 as originally wound, is Aslightly larger than the diameter ofthe holeSl..Y :Therefore, the countersunk portion 52 may extend a short distance downward beyond the rim V1S is order to facilitate the compression of the coil which occursif the mandrel is now driven down to locate the coil fullyinthe hole 51.k It has. been'found that it is preferableto drivethe mandrelLdown by Yrepeated Vtaps on its head rather than byV a continued pressure. The depth to which the coil, can be driven depends on the distance the .will be clear that'duringthe inserting operation, the coil pannot tilt nor otherwise deviate from its predetermined `form, first, owingntolthe fact thatonlaccount of the heli- @cal shape of the face 39, the axial thrust vby the mandrel is equally-distributed over; the `entire length of the top convolution of the coil;V j I n, thisconnection it is. to be :noted that whenthe compression'or Vcontraction 'of the Y ,convolutions entering' the hole 51 occurs, the convolutionsgwhich are still insidez the shell l17 will lengthen, wherefore-the end of the coil at the step V4,0 will turn Y 4 Y i somewhat. This turning, however, is directed against that step so that the entire top convolution remains in engagement with the surface 39. Secondly, the convolutions which are still inside the shell portion 17 are held co-axial with the hole 51 by that portion as the inner diameter of the latter is equal to the original outside diameter of those convolutions. Simultaneously, the shell prevents an expansion of the convolutions as a consequence of the axial compression. Thirdly, the convolutions which are contracted and are shifted insuch condition down the hole are prevented from tilting or other undesired deformation by the mandrel end 38, the vdiameter of which equals the inner diameter of the contracted convolutions. When the inserting process is completed, the tool will be withdrawn, and the resilient coil remaining in the hole in a compressed or contacted condition will set up a frictional resistance to forces tending to move it.

In certain instances', particularly with coils of relatively large cross-section, it will be preferable to combine with the tool according to the invention, a means for contracting the coil before it enters the cylindrical hole. Such means is shown in Fig. 6 in which the mandrel 60 is provided with a helical face 61 and step 62 similar to the face 39 and step 40 in Figs. l and 5. An end portion S0 projects downward from the face 61 in the same manner and for the'sarne purpose as the portion 38 in Figv l. The shell 63 guiding the mandrel in its' part at 64 along the` lateral recess 65, has a lower-endv66 the inner diameter of which decreases from the sizeof the outer diameter of the non-contracted lcoil to the size of the diameter of the hole 67 inthe boss 68. `A sharp edged rim 69 may project downward from the end face 70 similarly to the rim `15- in Fig. vl, so as to t'into the tiaring upper end 71 of the hole 67.

The modified tool according to Fig. 6 operates in substantially the same manner as the tool in Fig. 5 with the difference, however, that a coil 81v inserted in the recess 65 and held by the spring 82 will be engaged and pushed down by the mandred 60 in the lower portion 66 of the shell 63 where the coilwill be gradually contracted 1nefore'it enters the hole 67. The same result can, of course, be obtained if a separate piece, similar to theplower portion 66 of the shell of Fig'. 6 with suitably decreasing diameter, is inserted e. g. in Fig. 5 between ythe tool of Fig. 1 and the boss, provided the mandrel is made suiciently long.

It has been stated that the depth to which a coil can be inserted depends on' the distance between the face 39 in Fig. l from the face 16 when the mandrel head 27 Vbears on the shell end face 28. In order to render this distance adjustable, means may be provided e. g. as shown Vin Fig. 7 in which the upper end of themandrel 90 has an externally screw threaded extension 91. The mandrel head 92 is provided with an internal thread and screwed on the extension 91. A jam nut 93 may be applied in Y order to secure tllehead 92 in an adjusted position. Other Vmeans may be provided to adapt the tool ,to differently sized coils. Thus, the end portions 37 and 38 may be rendered exchangeable by making them separate pieces to be screwed into the end of the mandrel as indicated at 95 in Fig. 5.- Y

It Will be apparent to those skilled in the artthat many alterations and modifications of the structure shown and described may be made lwithout departure from the spirit and essence of the invention which for that reason "shall not be limited but byA the'scope of the appended claims.

I claim:

l. A tool for pushing a slightly oversized screw thread forming wire coil insert into a cylindrical hole while contracting'said coil to the diameter of said hole, comprising t a shell having a Ifoot end, and a vmandrel rotatable and axially movable in said shell s'o as to be retractable into and projectable from said foot end of said shell, the inner diameter of at least the lower portion of said shell being substantially equal to the outer diameter of said coil for which the tool is destined, so as to provide in said shell portion a sliding lit for the coil prior to its being contracted, the lower part of said mandrel including a first, a second and a third portion, the diameter of said second or median portion being smaller than that of said first portion which tits slidingly into said lower shell portion, and being larger than the diameter of said third or ultimate end portion whereby a shoulder vis formed between said third and said second portions, said second mandrel portion being of a diameter'tting the holeinto which said coil is to be inserted, and said third portion having a diameter substantially as large as but not larger than the inner diameter to which said coil is to be contracted, said shoulder having a helical face of a pitch corresponding to the pitch of said coil when its convolutions bear upon one another, and forming a step for engagement with the upper end of said coil when said third portion is introduced into the interior of said coil.

2. A tool as claimed in claim 1, said lower shell portion having an end face and including a small hollow frustro-conical extension co-axially projecting from said end face and adapted to engage a flaring end of thc'hole into which said coil is destined to be inserted. t

V3. A tool as claimed in claim 1, the wall in a part of said lower shell portion being provided with a lateral recess to receive therein said coil, and a resilient means secured to said wall so as to bear against said coil when in said recess thereby yieldingly to resist a movement of sa-id coil received in said recess. 7

4. A tool for pushing a slightly oversized screw thread forming wire coil'v insert into a cylindrical hole while contracting said coil to the diameter of said hole, comprising a shell having a foot end, and a mandrel rotatable said coil for which the tool is destined, so as to provide in said shell portion a sliding t for the coil prior to its being contracted, the lower part of said mandrel including a first, a second and a third portion, the diameter of said second or median portion being smaller than that of said first portion which titsl slidingly into said lower shell portion, and being larger than the diameter of said third or ultimate end portion whereby a shoulder is formed between said third and said second portions, said shoulder having a helical face of a pitch corresponding to the pitch of said coil when its convolutions bear upon one another, and forming a stop for engagement with the upper end of said coil when said third portion is introduced into the interior of said coil, in a portion of said shell adjacent the foot end portion thereof, the shell wall throughout half of its periphery being removed over a length somewhat more than the longest and axially movable in said shell so as to be retractable t into and projectable from said foot end of said shell, the inner diameter of at least the lower portion of said shell being substantially equal to the outer diameter of coil for which the tool is destined, so as to provide a recess, and said foot end portion being provided with a slot extending from said recess to the ultimate foot end of said shell, said tool further comprising a leaf spring secured to said adjacent portion so as to project into said recess and to retain said coil when inserted in said recess, and a spring wire secured to said leaf springr andgextending in said slot so as to bear against said coil when it is pushed through said foot end portion.

5. A tool as claimed in claim 4, said shell and said mandrel including abutment means so to limit the distance said mandrel can be retracted that its foot end clears said recess.

References Cited in the le of this patent UNITED STATES PATENTS 1,647,204 Susdorf Nov. 1, 1927'- 1,863,956A Wilson v. June 21, 1932 1,966,520 Rayner July 17, 1934 2,316,231 Evans Apr. 13, 1943 2,371,622 Hawkins Mar. 20, 1945 2,453,840 Geertsema Nov.. 16, 1948 2,513,792 Forster Iuly 4, 1950 

